Production of magnesium sulphide



Patented Sept. is, 1944- Theodore w. Sn... mm, Mich, minorto a The Dow'Chemical Company, Midland, Mioln,

a corporatlono! Michigan No Drawing. Application December 26, 1942, Serial No. 410.229.

ic'laims. (01. 23-134) This invention relates to an improvedmethod ofproducing magnesium sulphide.

As is known, magnesium sulphide has i been recommended as an agent in the control of metallurgical slags and fluxes, and as an ingredient in inorganic chemical syntheses. Despite these indications of promise, magnesium sulphide has never become a commercial material because of the difliculty of making it on any appreciable scale. In particular, the methods or preparation heretofore known have either involved serious explosion hazards, have been applicable only on a microchemical scale, have given exceedingly low yields of the material, or have required the use of rare and expensive starting reagents.

With these dimculties in mind, it is the principal object of the present invention to provide through the zone to expel air andany water present in the magnesium chloride. A stream of hydrogen sulphide is then forced through the zone while it-is still at a reaction temperature, for a time suflicient to convert the magnesium chloride to magnesium sulphide.

It is not essential, unless magnesium sulphide of extraordinary purity is required, that the magnesiumchloride used be anhydrous, since any waa-simple method of producing magnesium sulf phidein high yields from readily'availablematerials. Another obi'ect is to provide a processin which the magnesium sulphide obtained is in the crystalline state, instead of in the form of amorphous powder as heretofore.

The invention depends upon the discovery that dry magnesium chloride will react with dryhy-" drogensulphide to form crystalline magnesium sulphide, with simultaneous liberation :ofhydrogen chloride, as represented by the equation MgCh+ H:S MgS4 -2HC1 J In-making magnesium sulphide according to the new process, a cunent of gaseous hydrogen sulphide is passed into intimate contact with a body of magnesium chloride maintainedat a reaction temperature, usually between about 700 C. and about 900 0., for a time sumcient to convert it to magnesium sulphide, usually for 2to- 10 hours or more, depending upon the physical state of the magnesium chloride. During the process, hydrogen chloride is continuously formed" as a gasand is withdrawn-while the-magnesium sulphide produced remains in the reaction zone tion but is not to ter of hydration present will be driven ofl in the early-stages of the process. This evolution of water does not interfere with subsequent formation of magnesium sulphide, but may tend to form a small proportion of magnesium'oxide which is not disadvantageous for many of the uses to which magnesiumsulphide is placed.

The following example will illustrate the inven- Example A mass of crude anhydrous magnesium chloride (containing 83.6 per cent magnesium chloscope ride,"-13 per cent magnesium oxide, balance mostin the form oi a crystalline mass of pinkish-white 5 color.. The process ispreferably carried out in the absence of moisture and oxidizing agents to avoid converting any or the sulphide formed to magnesium oxide. i

In a particularly convenient form of the. process, magnesium chloride is charged into the reaction zone, which may be an externally-heated tube furnace or rotary kiln; and heated to a team-- 'cent magnesium chloride.

,ly water) was charged intoa tube furnace heated to a temperature or 700 C. while dry hydrogen sulphidev was passed through the furnace until all water present was removed, The flow of hydrogen sulphide was thencontinued at 750 C.

for 8 hours, after which the Iurnace was cooled- "to "room temperature while continuing the flow of gas. -'-Ihe product obtained was a crystalline powder containing 89.2 per cent magnesium sulphide, 8.3 per cent magnesium oxide If it is desired to produce mixtures of magnesium sulphide and magnesium chloride, such as have beenrecommended for use in the electrolytic production of magnesium, these may be readily prepared according to theinvention simply by discontinuing the reaction of hydrogen sulphide with magnesium chloride before the latter is entirely consumed.

Other modes of applying. the principle of the invention may be employed instead of those explained, change being made as regards details. provided the steps recited in any of the following claims or the equivalent thereof are used.

perature of 700. .to- 900 C., and a-current of hydrogensulphide or a 'dry gas chemicallyl inert to magnesium chloride, such ashydrogen chloride, nitrogen, hydrogen, or a' nob le gas, ispassed I claim: a 1. A method of preparing magnesium sulphide which comprises passing hydrogen sulphide into contact with "anhydrous magnesium chloride maintained at a reaction temperature above about 700 C. so as to produce magnesium sulphide.

2. A method of preparing magnesium sulphide be construed'as limiting its and 1.8 per which comprieee e. current'oi dry hy- .drogen mlpmde into intimate contact with a. body of anhydrous mngneeium chloride maintained at e reaction tunpereture above about "100 C.-un'der non-oxidiring conditione'eo as to produce megl neeium' sulphide ind; hydrogen chloride: end withdrawing the hydrogen chloride on it in formed. g

3. A method according to claim 2 wherein the ture between about 700' C. end about 900' O.

4. A method of m rine munerium sulphide .umetoezpellnyweterpreeenttheremend thereeiterpeeeingecurrentotbydrogenmiphide into intimlte 00M Ilth the lid chloride while meinteiningeeidtempentureeoel to produce megneeium eul'phide and hydrogen chloride is maintained at a tempere- 1O chloride; and withdrew h hymen chlorid A :EBARIGI. 

